Gas planning and the associated math - controversies over need and how to teach

[Melicertes]

People get the wits scared out of them about DCS, but running out of gas and drowning is much more final. Running out of gas and embolizing is, too.

I'm with TSandM on this one. Personally I cannot see why an OW diver cannot be taught to understand at least the very basic (I am not saying complex) concepts of gas management principles and encouraged to incorporate it into their dive planning. Seriously, I've been a PADI tadpole for all of my diving career and I have yet to see a diving group do any dive planning at a resort of any kind that would suggest that they are even taking note of the nitrogen lodading levels with the RDP. OK, maybe the couple that completed their course yesterday still does it but what about those that did it last month? Most people I've seen are happy to go on the set diving schedule that the resort sets up and that hopefully incorporates some decent SIT but other than that they're either diving their 'puters or they just don't care and come up when their gas hits 50bar or whatever minimum they've been taught to observe (or the Dm on the dive says is the sweet spot for that particular dive).

I hear and totally agree with NWGratefulDiver's assertion that students have to make that paradigm shift from focussing on what gas they end up with to anticipating what they will need proactively. And for this, no matter how bad your math skills are, I feel where there's a will there's a way. But because most people hate math because everyone says it's so difficult, they never get to even start thinking for themselves beyond what a table says or what the DM says, or heck doing what they did the last time that worked for that matter.

People are way smarter than they will admit and with a little effort and the right support from a competent instructor I see absolutely no reason why the new OW diver should not have at least a good grasp on gas managment principles. Now when it comes to advanced this becomes, for me personally, a no-brainer. We're happy to teach them about oxygen toxicity and MODs etc. when diving nitrox (which is becoming ever more accessible to everyone these days) but heaven forbid they cannot do the same basic analysis with normal gas management on air.

I say raise the bar. Maybe do not necessarily require gas management as a requirement in OW but at the very least teach it and reinforce the importance of it, then build on that introduction in advanced and make it a mandatory skill that has to be mastered for a AOW cert to be issued. It's not that hard people.

 

[Melicertes]

Running out of gas on scuba is not a life or death emergency either. You did have some plan for redundancy, didn't you??? If not, better take another look at golf.

I do yes, because I plan my dive and gas requirements beforehand. And standing beside the road waiting for the AAA to pitch up with a gas can to tie you over to reach the next gas station is not a life or death emergency, you could sit there safely all day if necessary (I'm not going into hypothetical situations here about political situations in certain countries so don't go there). Run out of breathing gas when you're at 60ft because you didn't plan or keep an eye on your gauge sitting there sure as pete becomes a life or death emergency IMHO. What prevents you from soffocating at that point depends on how you respond, but it nevertheless remains a very clear and present danger to your continued survival; i.e. a life or death situation.

Weeelll, ok so maybe you do a CESA and happen to make it out OK; if you embolize you may have tons of breathing gas at the surface but you're still going to hope the gods don't downthumb you as an outcome of your embolism. Maybe you make it without complications, I say you were lucky. What about next time? Running out of breathing gas is IMHO a life or death emergency.

Edit: Besides, I hate golf.

 

[Thalassamania]

I use the car analogy often. If you can teach someone how not run out of gas in a car, the extension to diving is rather simple. Distance is time, speed is sac rate, gas gauge is SPG. There's even the starting simile of a j-valve with the old no gas gauge, reserve lever on the floorboard. Gas can = pony bottle. ESE = staying within walking distance of home (e.g., shallow). Spare Air = just enough gasoline to restart engine. etc.

 

[vshearer]

Just let the Internet do their thinking for them.

Gas Consumption

SAC Calculator

 

[SparticleBrane]

I use the car analogy often. If you can teach someone how not run out of gas in a car, the extension to diving is rather simple. Distance is time, speed is sac rate, gas gauge is SPG. There's even the starting simile of a j-valve with the old no gas gauge, reserve lever on the floorboard.

We also talk about how different size gas tanks tell you nothing without proper units, just as differences in PSI are different for every kind of cylinder.

 

[Gombessa]

I use the car analogy often. If you can teach someone how not run out of gas in a car, the extension to diving is rather simple. Distance is time, speed is sac rate, gas gauge is SPG. There's even the starting simile of a j-valve with the old no gas gauge, reserve lever on the floorboard. Gas can = pony bottle. ESE = staying within walking distance of home (e.g., shallow). Spare Air = just enough gasoline to restart engine. etc.

The problem is in a lot of places, it's pretty hard to not have a gas station around when you need it. No matter where I'm going, I just start driving there, and when I need gas I pull over at the next station. Sometimes that's at half a tank, sometimes the needle is past E. Never have I been worried about running out of gas (and never have I come close to running out). I have a feeling most people drive like this, and have never run out of gas either. In this sense, typical driving habits are more akin to "ascend with 500psi" than any kind of proper gas planning.

 

[SparticleBrane]

The problem is in a lot of places, it's pretty hard to not have a gas station around when you need it. No matter where I'm going, I just start driving there, and when I need gas I pull over at the next station. Sometimes that's at half a tank, sometimes the needle is past E. Never have I been worried about running out of gas (and never have I come close to running out). I have a feeling most people drive like this, and have never run out of gas either. In this sense, typical driving habits are more akin to "ascend with 500psi" than any kind of proper gas planning.

On the other hand there's people who can tell you within just a few miles how much further their car can go. And yes, I do plan my trips around that, or at least something along the lines of "I can go 300 more miles, let's get gas 200-250 miles from now."

 

[Gombessa]

On the other hand there's people who can tell you within just a few miles how much further their car can go.

I do exactly that as well, (I write down and track my mpg and driving profile at every fill-up, if you can believe that). Still, the way I approach fills is passive/reactive - I don't say "My trip is 100 miles, I have 2/3 tank, that gives me 225 miles, so I'll fill up within 5 miles of reaching my destination so I can get home with 200 miles remaining..." Instead, I start driving, and at some point look at the gauge and say "OK, I should get a fill within the next 5/10/50 miles." To me, that's a lot more like jumping into the water, looking at your spg every few minutes and deciding how long you can stay down before ascending with 500psi remaining.

When I set up for a dive, I'm much more proactive. I think about the dive profile, use rock bottom, make additional reserves for contingencies like swimming under kelp, etc.

I just think that people probably drive more like me than like you, and as such, planning a dive like I'd plan a car trip is the wrong message to send

 

[NudeDiver]

I've met successful people who still (in their late 20's) struggle with pre-algebra.

I know a university graduate who struggles with the basic math involved in calculating points during a game of dominoes.

Are you saying that these people shouldn't be divers since they don't get the ridiculous mathematical calculation of air consumption well enough?

She teaches math to elementary students. I don't think she should be.

 

[MXGratefulDiver]

If my wife/buddy had to do gas calculations in order to dive, I'd be doing all my diving solo. I see nothing wrong with presenting the concept as there are folks who can and will use it. But there is a lot of perfectly safe recreational diving that can be planned and executed without gas calculation.

How many folks driving down the highway do you think have planned their trip based on fuel consumption rates and fuel capacities? Their planning probably does not go much further than knowing, from experience, whether they will have to stop and get gas or not.

Great analogy ... but considering there aren't any available "gas stations" underwater, a better analogy would be that you're about to go driving across the desert (where, if you run out of gas the chances of dying are pretty good) ... you see a sign that says "Next Gas 163 Miles".

Think you'd stop to do a coupla quick calculations and see if you had enough to make it?

... Bob (Grateful Diver)